Use a paint remover, then plan to do some sanding, find the wood has very plain grain and apply some sort of finish and sand some more. In the end it will be a lot of work for a very plain looking stock that might look gosh awful.
Personally if I didn't care for the camo I'd pick a paint color I liked. I've used various colors of Krylon stone finish on rough duty milsurp stocks and have been happy with the results.
Simple, direct, and correct...
